<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<style>
	.item{
		width: 100px;
	    padding-top: 100px;
		position: relative;
	}
	.li{
		position:absolute;
		width: 100%;
		height: 100%;
		top: 50%;
	    left: 0;
	    display: flex;
	    align-items: center;
	    flex-direction: column;
	    transform: translateY(-50%);
		background-color: aqua;
		z-index: 10;
	}
	</style>
	<body>

		
		<div class="item">
			<div class="li" id="dom">
				
			</div>
		</div>
		
		<script>
			let dom=document.getElementById('dom');
			
			
		</script>
	</body>
</html>